1. Technical Field
This invention relates generally to seal assemblies, and more particularly to rotary shaft seal assemblies having a PTFE seal lip.
2. Related Art
Shaft seals are commonly used throughout numerous types of vehicle applications. Aside from the shaft seal establishing a reliable seal against a running surface of a rotating shaft or wear sleeve, both to prevent the ingress of contamination and the egress of desirable lubrication, it is desirable that the seal provide a minimal running torque against the shaft. A reduced running torque of the seal helps to enhance the overall fuel economy of the vehicle, as lower torque requires less parasitic horse power to turn the shaft, such as a crankshaft, for example, due to less drag produced by the shaft seal against the running surface of the shaft. As such, it is known to use low friction materials to provide seal lips for engagement with the running surface. One such known material is polytetrafluoroethylene (PTFE). In order to achieve an optimal seal, it is desired to provide a sealing surface on the PTFE seal lip as the sole, active portion forming the seal. Further, it is desirable to control the flexing of the PTFE seal lip in use, thereby allowing a reliable seal to be attained.